What is required for reflection with normal incidence?

What is required for reflection with normal incidence?

• A. Total internal reflection
• B. The use of Snell's law
• C. Different impedances are required
• D. The same impedances

Answer: (C)

Reflection at normal incidence depends on impedance mismatch between the two media. When the intrinsic impedances Z1 and Z2 differ, part of the wave is reflected; the reflection strength is given by a coefficient proportional to (Z2 − Z1)/(Z2 + Z1). If the impedances are the same, this coefficient is zero and no reflected wave occurs, so all the energy is transmitted. Therefore, having different impedances is what allows reflection to happen at normal incidence. Snell’s law governs how the wave bends (refraction) and, at normal incidence, there is no bending at all; it doesn’t by itself require or cause reflection. Total internal reflection is a phenomenon that happens only at certain angles when moving from a higher to a lower index medium, which does not apply at normal incidence.

Reflection at normal incidence depends on impedance mismatch between the two media. When the intrinsic impedances Z1 and Z2 differ, part of the wave is reflected; the reflection strength is given by a coefficient proportional to (Z2 − Z1)/(Z2 + Z1). If the impedances are the same, this coefficient is zero and no reflected wave occurs, so all the energy is transmitted. Therefore, having different impedances is what allows reflection to happen at normal incidence. Snell’s law governs how the wave bends (refraction) and, at normal incidence, there is no bending at all; it doesn’t by itself require or cause reflection. Total internal reflection is a phenomenon that happens only at certain angles when moving from a higher to a lower index medium, which does not apply at normal incidence.